Closing the Gap: Global Potential for Increasing Biofuel Production Through Agricultural Intensification

In the past couple of decades, the global agricultural industry has seen a massive boom, in part due to a combination of fertilizers, pesticides, herbicides, smart management techniques, mechanization, irrigation, and optimized seed varieties and genetic engineering.  This jump in agriculture not only provides the opportunity to feed our growing population, but to also create ethanol and biodiesel to meet our energy demands.  Johnston et al. (2011) looked at the magnitude and spatial variation of new agricultural production potential from closing of ‘yield gaps’ for 20 major ethanol and biodiesel crops.  By using data sets of annual crop yields to determine the amount of additional biofuel produced from obtaining yield gaps up to the global median yield, the researchers deduced that approximately 112.5 billion liters of ethanol and 8.5 billion liters of biodiesel could be made.  While this shows an optimistic future for energy security, it also has a profound effect on policymakers and how individuals will determine goals of reaching a level of biofuel use.  —Anthony Li
Johnston M., Licker R., Foley J., Holloway T., Mueller N. D., Barford C., Kucharik C. 2011. Closing the gap: global potential for increasing biofuel production through agricultural intensification. Environmental Research Letters 6, 034028

The authors of this paper investigated 20 common biofuel and biodiesel crops, some notable ones include maize, rice, sugarcane and wheat for biofuel, or ethanol, and soybean, rapeseed, and oil palm for biodiesel crops.  The researchers obtained the M3 data set of global farming yields for these 20 crops and organized the data based on region.  With information on the average global yields of crops, the authors were able to calculate the yield gaps, which they defined for this study as the “difference between current agricultural yields and future potential based on climatic and biophysical characteristics of the growing region.”  They calculated the potential yields of biodiesel and ethanol if yield gaps of these crops were closed to multiple degrees, such as the global median or the 90thpercentile gap of what is completely attainable.  In order to observe the effects of unequal distributions of irrigation infrastructure and sustainable water resources on crop yields, the researchers re-ran their analysis with irrigated areas excluded.  In order to get a rough idea of what was needed to increase crop yield, the authors calculated the growing degree days for each crop, which is a measure of heat to predict plant development rates.
The researchers found that increasing yield gaps to the median global yield would result in 112.5 billion additional liters of ethanol and 8.5 billion liters of ethanol, while obtaining the 90th percentile gap would result in 450 billion liters of additional ethanol and 33 billion liters of biodiesel.  While the new tonnage varied considerably between biodiesel and ethanol, the overall percentage increase between the two were roughly equal, ranging from 10%–17%.  The majority of ethanol potential identified was attributable to maize, wheat, and rice crops, while the majority of biodiesel potential was attributable to soybean, rapeseed, and oil palm.  Biodiesel fuel production was generally more evenly distributed amongst its constituent crops, whereas ethanol fuel production was incredibly uneven between the crops.
The implications of this study in energy security are obvious, but they also provide a benefit to policymakers or anyone setting goals for biofuel use.  The research performed here shows policymakers how much additional biofuel we can expect from closing various yield gaps to different degrees, allowing them to make more accurate goals.  For example, The Renewable Fuel Standard Program Final Rule of the 2007 Energy Independence and Security Act made a goal for the US to blend 36 billion gallons of biomass-based fuels by 2022.  As ambitious as this goal was, this study showed that even if all the countries were to increase their biofuel crop yields to only the median level, there would still not be enough fuel to meet this goal.  This study is also useful in that it shows the biofuel and biodiesel distribution based on specific crop.  For ethanol, a very notable crop for fuel production was sugarcane.  While this may not mean that sugarcane produces the most ethanol of any other crop per mass, if we can identify whichever crop produces more fuel than others, we can focus our biofuel industry to take advantage of these specific crops.
In the face of our energy and food crisis, our nations should begin looking towards agriculture for potential solutions.  Johnston et al.’s study shows how much additional biofuel can be produced by closing various yield gap levels per crop.  This information will prove useful to governments seeking to implement goals of reaching certain levels of biofuel use and individuals such as farmers who want to capitalize on the most biofuel yielding crop.

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